[tomek]

hi gang, i'll be needing a preamp for a new power amp that i'm buying for my speaker rig and i'm not sure what do do about a preamp.

i've heard both good and bad things about passive preamps.

some say it's the purest way to get the signal through, while others say the impedance matching problems cause poor sound.

what do you guys have to say?

 

[DarkAngel]

If you only want simple system with one source and amp then a well designed passive will work extremely well especially if matched to output/input levels of source/amp.

At Audiogon I got a killer passive LAT (luminous audio tech) with custom dual volume controls (actually variable shunts) and values matched to my gear. Get the caddock resistor upgrade if you try one:

LAT


Here is pix of my custom unit in action, dual volume controls/caddock raised price to $225:

 

[sacd lover]

I have used passive preamps for years; they can sound great. You just need to be sure your source is capable of driving the interconnect cables and the input impedence of your amp.

 

[philodox]

Question: Would the famous 'hot' output of the ART DI/O actually be a benifit with a Passive Preamp?

 

[tomek]

my source will actually be the Behringer DEQ2496, but with 1.5m XLR to RCA cables from source to preamp so i'm worried about the length of the cables. my preamp to amp cables will be 20cm long.

however, the Behringer has a gain control so perhaps it would be alright. i know its output was quite a bit higher than my Teac cd player's.

 

[Wodgy]

1.5m cables are too long for use with a passive preamp.

 

[lan]

What is a good length of cable then? What happens if the cable is too long?

 

[philodox]

And are we talking the cable from the source to passive preamp as well as the cable from the passive preamp to the amp?

I'm wondering if my passive preamp with 3 source selector and 3 output selector might be a bad idea now since I wont be able to get the cable lengths short enough...

 

[tomek]

1.5m is from the source to the preamp. i heard that was not as critical.

i have custom cables from preamp to amp that are about 20cm long.

i'm not sure what to do about those other cables. i'd have to do something custom as well to get as short a run as possible, but does it matter that much?

 

[sacd lover]

Quote:

Originally Posted by tomek 1.5m is from the source to the preamp. i heard that was not as critical. i have custom cables from preamp to amp that are about 20cm long. i'm not sure what to do about those other cables. i'd have to do something custom as well to get as short a run as possible, but does it matter that much?

I ran a 1.5m cable from the source to the passive preamp and then a 1.0m cable from the passive to the amp without any problems at all. Runs of cable that are to long and/or high capacitance can roll of the treble. A low capacitance cable will help. How robust the output from your source is has a good deal to do with how well this works too.

 

[JaZZ]

My cables are 30 and 40 cm between source and passive attenuator and 2.30 m between the latter and the power amp. No problem at all and great sound. I got a similar sonic balance with an active preamp (Prehead MkII) -- which proves that this length isn't critical in my setup.

What's important apart from cable length and capacitance is the ratio between source output impedance and power-amp input impedance. It should be as high as possible. My main source, the Bel Canto DAC2, has 20 ohm, the Metaxas Solitaire has 100 kOhm, making a ratio of 2000.That's a huge number. But I also got good results with my Hitachi FM tuner (2 kOhm) and my BEL 1001 power amp (20 kOhm), thus a ratio of 10, with the same cable lengths. But this could indeed be a little close for a perfectly neutral sonic balance.

In my experience nothing beats passive amps in an electrically favorable system when it comes to signal accuracy and sonic purity. In an uncritical environment all «improvements» resulting from an active preamp are in fact euphonic colorations. But one thing must be taken into consideration: the passive variant can be too revealing in certain cases.

 

[lini]

tomek: How many sources do you intend to connect to your preamp? If it's only one, why not mod your new poweramp and integrate a pot right into it? That would eliminate superfluous transitions and be cheaper than a passive preamp as well...

Greetings from Hannover!

Manfred / lini

 

[BaddogAudio]

Why do you say that, 1.5 meters is not that long and it really depends on your source and the type of cables.

 

[V1001]

Passive preamps are to die for when done right. I could never ever go back to an active preamp. Actually getting rid of preamps all together was the best move I ever made Since I go direct to my amps from my DAC now. It's been ages since I've moved on from my passive even. That's the beauty of using a PC with software volume control. There is just no comparison to how pure and unbelievably clean and real the sound is not having the signal have to go through a preamp and an extra set of cables. But a passive will get you closer to that and is far better too. 
 
Anyway yeah always use XLR. Since balanced out has higher voltage. Also if you want to try it out first to get an idea of if it's going to work or not and how it will sound, just hook directly from your source to your amp. Put on a very soft and quiet song that maybe builds louder and louder. Because you'll basically be running full blast. It's not a problem though if the song is mellow and quiet. The first time I did that my jaw dropped. And I said goodbye to active preamps. This will  tell you also if you like your amp and DAC sound since you'll be hearing them in there purest form and not using a preamp to gloss over or fix some issue in the sound of them. 

 

[FieldEffect]

Well, even though this thread is 12 years old, I'll throw in my 2 cents. I use a passive preamp between my PC and my studio monitors. I have a 3ft cable from the PC to the preamp, and then 10ft cables from the preamp to the monitors. Everything sounds very good to me, much better than when I was using a powered mixer for a volume control.
 
I do wish I understand impedance matching better, though. The ALPS pot in my preamp is a 10k model. I have no idea what the output impedance of my PC's sound jack, or what the input impedance is of my studio monitors, so I don't know what an ideal pot would be. I could have got 50k or 100k, but I was just told to go with 10k if in doubt.
 
I also started another thread asking for input on pots vs stepped attenuators a few days ago, but I haven't got any replies to that. If anyone feels like chiming in, I'd appreciate it. My thread is 12 years newer.
 
Cheers.